Message-ID: <3135968.eiNgRHp3gn@aspire.rjw.lan>
Date:   Fri, 14 Sep 2018 11:21:17 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Pavel Machek <pavel@....cz>,
        Rui Zhang <rui.zhang@...el.com>,
        Chen Yu <yu.chen.surf@...il.com>,
        Zhimin Gu <kookoo.gu@...el.com>,
        Len Brown <len.brown@...el.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 3/4][v2] x86, hibernate: Extract the common code of 64/32 bit system

On Tuesday, September 11, 2018 7:20:46 PM CEST Chen Yu wrote:
> From: Zhimin Gu <kookoo.gu@...el.com>
> 
> Reduce the hibernation code duplication between x86-32 and x86-64
> by extracting the common code into hibernate.c.
> 
> No functional change.
> 
> Acked-by: Chen Yu <yu.c.chen@...el.com>
> Acked-by: Pavel Machek <pavel@....cz>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Zhimin Gu <kookoo.gu@...el.com>
> ---
>  arch/x86/power/hibernate.c        | 265 ++++++++++++++++++++++++++++++
>  arch/x86/power/hibernate_32.c     |  23 +--
>  arch/x86/power/hibernate_64.c     | 246 +--------------------------
>  arch/x86/power/hibernate_asm_64.S |   2 +-
>  4 files changed, 269 insertions(+), 267 deletions(-)
>  create mode 100644 arch/x86/power/hibernate.c
> 
> diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c
> new file mode 100644
> index 000000000000..6aeac4d3c9df
> --- /dev/null
> +++ b/arch/x86/power/hibernate.c
> @@ -0,0 +1,265 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Hibernation support for x86
> + *
> + * Copyright (c) 2007 Rafael J. Wysocki <rjw@...k.pl>
> + * Copyright (c) 2002 Pavel Machek <pavel@....cz>
> + * Copyright (c) 2001 Patrick Mochel <mochel@...l.org>
> + */
> +
> +#include <linux/gfp.h>
> +#include <linux/smp.h>
> +#include <linux/suspend.h>
> +#include <linux/scatterlist.h>
> +#include <linux/kdebug.h>
> +#include <linux/bootmem.h>
> +
> +#include <crypto/hash.h>
> +
> +#include <asm/e820/api.h>
> +#include <asm/init.h>
> +#include <asm/proto.h>
> +#include <asm/page.h>
> +#include <asm/pgtable.h>
> +#include <asm/mtrr.h>
> +#include <asm/sections.h>
> +#include <asm/suspend.h>
> +#include <asm/tlbflush.h>
> +#include <asm/mmzone.h>
> +
> +/* Defined in hibernate_asm_64.S or hibernate_asm_32.S */
> +extern asmlinkage __visible int restore_image(void);
> +
> +/*
> + * Address to jump to in the last phase of restore in order to get to the image
> + * kernel's text (this value is passed in the image header).
> + */
> +unsigned long restore_jump_address __visible;
> +unsigned long jump_address_phys;
> +
> +/*
> + * Value of the cr3 register from before the hibernation (this value is passed
> + * in the image header).
> + */
> +unsigned long restore_cr3 __visible;
> +unsigned long temp_pgt __visible;
> +unsigned long relocated_restore_code __visible;
> +
> +#ifdef CONFIG_X86_32
> +	#define RESTORE_MAGIC	0x12345678UL
> +#else
> +	#define RESTORE_MAGIC	0x23456789ABCDEF01UL
> +#endif
> +
> +/**
> + * pfn_is_nosave - check if given pfn is in the 'nosave' section
> + * @pfn:	the page frame number to be checked
> + *
> + * returns non-zero if the pfn is in the 'nosave' section,
> + * otherwise returns zero
> + */
> +int pfn_is_nosave(unsigned long pfn)
> +{
> +	unsigned long nosave_begin_pfn;
> +	unsigned long nosave_end_pfn;
> +
> +	nosave_begin_pfn = __pa_symbol(&__nosave_begin) >> PAGE_SHIFT;
> +	nosave_end_pfn = PAGE_ALIGN(__pa_symbol(&__nosave_end)) >> PAGE_SHIFT;
> +
> +	return pfn >= nosave_begin_pfn && pfn < nosave_end_pfn;
> +}
> +
> +#ifdef CONFIG_X86_64
> +static int relocate_restore_code(void)
> +{
> +	pgd_t *pgd;
> +	p4d_t *p4d;
> +	pud_t *pud;
> +	pmd_t *pmd;
> +	pte_t *pte;
> +
> +	relocated_restore_code = get_safe_page(GFP_ATOMIC);
> +	if (!relocated_restore_code)
> +		return -ENOMEM;
> +
> +	memcpy((void *)relocated_restore_code, core_restore_code, PAGE_SIZE);
> +
> +	/* Make the page containing the relocated code executable */
> +	pgd = (pgd_t *)__va(read_cr3_pa()) +
> +		pgd_index(relocated_restore_code);
> +	p4d = p4d_offset(pgd, relocated_restore_code);
> +	if (p4d_large(*p4d)) {
> +		set_p4d(p4d, __p4d(p4d_val(*p4d) & ~_PAGE_NX));
> +		goto out;
> +	}
> +	pud = pud_offset(p4d, relocated_restore_code);
> +	if (pud_large(*pud)) {
> +		set_pud(pud, __pud(pud_val(*pud) & ~_PAGE_NX));
> +		goto out;
> +	}
> +	pmd = pmd_offset(pud, relocated_restore_code);
> +	if (pmd_large(*pmd)) {
> +		set_pmd(pmd, __pmd(pmd_val(*pmd) & ~_PAGE_NX));
> +		goto out;
> +	}
> +	pte = pte_offset_kernel(pmd, relocated_restore_code);
> +	set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_NX));
> +out:
> +	__flush_tlb_all();
> +	return 0;
> +}
> +
> +#define MD5_DIGEST_SIZE 16
> +
> +struct restore_data_record {
> +	unsigned long jump_address;
> +	unsigned long jump_address_phys;
> +	unsigned long cr3;
> +	unsigned long magic;
> +	u8 e820_digest[MD5_DIGEST_SIZE];
> +};
> +
> +#if IS_BUILTIN(CONFIG_CRYPTO_MD5)
> +/**
> + * get_e820_md5 - calculate md5 according to given e820 table
> + *
> + * @table: the e820 table to be calculated
> + * @buf: the md5 result to be stored to
> + */
> +static int get_e820_md5(struct e820_table *table, void *buf)
> +{
> +	struct crypto_shash *tfm;
> +	struct shash_desc *desc;
> +	int size;
> +	int ret = 0;
> +
> +	tfm = crypto_alloc_shash("md5", 0, 0);
> +	if (IS_ERR(tfm))
> +		return -ENOMEM;
> +
> +	desc = kmalloc(sizeof(struct shash_desc) + crypto_shash_descsize(tfm),
> +		       GFP_KERNEL);
> +	if (!desc) {
> +		ret = -ENOMEM;
> +		goto free_tfm;
> +	}
> +
> +	desc->tfm = tfm;
> +	desc->flags = 0;
> +
> +	size = offsetof(struct e820_table, entries) +
> +		sizeof(struct e820_entry) * table->nr_entries;
> +
> +	if (crypto_shash_digest(desc, (u8 *)table, size, buf))
> +		ret = -EINVAL;
> +
> +	kzfree(desc);
> +
> +free_tfm:
> +	crypto_free_shash(tfm);
> +	return ret;
> +}
> +
> +static int hibernation_e820_save(void *buf)
> +{
> +	return get_e820_md5(e820_table_firmware, buf);
> +}
> +
> +static bool hibernation_e820_mismatch(void *buf)
> +{
> +	int ret;
> +	u8 result[MD5_DIGEST_SIZE];
> +
> +	memset(result, 0, MD5_DIGEST_SIZE);
> +	/* If there is no digest in suspend kernel, let it go. */
> +	if (!memcmp(result, buf, MD5_DIGEST_SIZE))
> +		return false;
> +
> +	ret = get_e820_md5(e820_table_firmware, result);
> +	if (ret)
> +		return true;
> +
> +	return memcmp(result, buf, MD5_DIGEST_SIZE) ? true : false;
> +}
> +#else
> +static int hibernation_e820_save(void *buf)
> +{
> +	return 0;
> +}
> +
> +static bool hibernation_e820_mismatch(void *buf)
> +{
> +	/* If md5 is not builtin for restore kernel, let it go. */
> +	return false;
> +}
> +#endif
> +
> +/**
> + *	arch_hibernation_header_save - populate the architecture specific part
> + *		of a hibernation image header
> + *	@addr: address to save the data at
> + */
> +int arch_hibernation_header_save(void *addr, unsigned int max_size)
> +{
> +	struct restore_data_record *rdr = addr;
> +	int ret = -EINVAL;
> +
> +	if (max_size < sizeof(struct restore_data_record))
> +		return -EOVERFLOW;
> +	rdr->jump_address = (unsigned long)restore_registers;
> +	rdr->jump_address_phys = __pa_symbol(restore_registers);
> +
> +	/*
> +	 * The restore code fixes up CR3 and CR4 in the following sequence:
> +	 *
> +	 * [in hibernation asm]
> +	 * 1. CR3 <= temporary page tables
> +	 * 2. CR4 <= mmu_cr4_features (from the kernel that restores us)
> +	 * 3. CR3 <= rdr->cr3
> +	 * 4. CR4 <= mmu_cr4_features (from us, i.e. the image kernel)
> +	 * [in restore_processor_state()]
> +	 * 5. CR4 <= saved CR4
> +	 * 6. CR3 <= saved CR3
> +	 *
> +	 * Our mmu_cr4_features has CR4.PCIDE=0, and toggling
> +	 * CR4.PCIDE while CR3's PCID bits are nonzero is illegal, so
> +	 * rdr->cr3 needs to point to valid page tables but must not
> +	 * have any of the PCID bits set.
> +	 */
> +	rdr->cr3 = restore_cr3 &(~CR3_PCID_MASK);
> +
> +	rdr->magic = RESTORE_MAGIC;
> +
> +	ret = hibernation_e820_save(rdr->e820_digest);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +/**
> + *	arch_hibernation_header_restore - read the architecture specific data
> + *		from the hibernation image header
> + *	@addr: address to read the data from
> + */
> +int arch_hibernation_header_restore(void *addr)
> +{
> +	struct restore_data_record *rdr = addr;
> +
> +	restore_jump_address = rdr->jump_address;
> +	jump_address_phys = rdr->jump_address_phys;
> +	restore_cr3 = rdr->cr3;
> +
> +	if (rdr->magic != RESTORE_MAGIC) {
> +		pr_crit("Unrecognized hibernate image header format!\n");
> +		return -EINVAL;
> +	}
> +
> +	if (hibernation_e820_mismatch(rdr->e820_digest)) {
> +		pr_crit("Hibernate inconsistent memory map detected!\n");
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +#endif
> diff --git a/arch/x86/power/hibernate_32.c b/arch/x86/power/hibernate_32.c
> index afc4ed7b1578..e0e7b9aea22a 100644
> --- a/arch/x86/power/hibernate_32.c
> +++ b/arch/x86/power/hibernate_32.c
> @@ -6,17 +6,7 @@
>   * Copyright (c) 2006 Rafael J. Wysocki <rjw@...k.pl>
>   */
>  
> -#include <linux/gfp.h>
> -#include <linux/suspend.h>
> -#include <linux/bootmem.h>
> -
> -#include <asm/page.h>
> -#include <asm/pgtable.h>
> -#include <asm/mmzone.h>
> -#include <asm/sections.h>
> -
> -/* Defined in hibernate_asm_32.S */
> -extern int restore_image(void);
> +#include "hibernate.c"

I don't particularly like this.

Why excatly do you need to include the C file here?

Also, the way this change is made makes it quite hard to review, as the
new code is not exactly the same as the code being removed, so it is
hard to say whether or not there really are no functional changes
as claimed.

This is sensitive code, mind you, and really hard to debug if anything goes
wrong.  Please be super-careful about changing it.

Thanks,
Rafael

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